databases

Question 1

what is ACID

Answer 1

required properties for database services, ensuring that it is efficient and safe to use.
Atomicity - each dataset is divided into smallest indivisible parts (adress is divided into town and street for example.)
Consistency - ensuring that the service is consistent (if you draw 3000 eur out of your bank account you dont want to get 20 do you.)
Isolation - concurency control; in case few transactions will try to pass at the same time, consistency will ensure that each are treated individually (“first come first served”)
Durability - ensures that the data is not lost (bank explodes ☹️ but you’re still rich with the saved money in it 🤑)

Question 2

data dictionary

Answer 2

what fields are what type (phone is TEXT field for example)

Question 3

boolean

Answer 3

binary - yes/no; 1/0

Question 4

forms

Answer 4

in google forms for example the thing

Question 5

query

Answer 5

a type of search - searching “databases” in google docs is a simple query. searching “databases” and adding “used by Jernej Fegus” is a complex query, as it involves simple logic.

Question 6

ERD

Answer 6

entity-relationship diagram (the full database tables with the keys attached to eachother)

Question 7

transaction

Answer 7

a sequence of operations - entire sequence is one logical unit of work

states:
active comes into either failed or particularly commited. fail ends in aborted.
particularly commited can go into either failed or end in a committed state.

Question 8

table

Answer 8

2d array/grid with rows and columns

Question 9

fields and records

Answer 9

columns and rows. take time to imagine a form and how answers of it would be organised.

Question 10

primary key

Answer 10

unique, like IDs

Question 11

secondary key

Answer 11

fiekd categories like Names (there are many names)

Question 12

indexing

Answer 12

like indexing book topics

Question 13

foreign key

Answer 13

imported primary key

Question 14

super key

Answer 14

composite key = key + key

for example costumersID and ordersID make up prices (can be different prices despite the fact that costumers can be same)

Question 15

what kind of relationship are available in databases

Answer 15

one to one (one child has one biological mother)
one to many (one mother can have many children)
many to many (TO BE AVOIDED IN GOOD DATABASE DESIGN!!)
orphan data (ALSO TO BE AVOIDED AS IT IS INEFFICIENT)

Question 16

what is the hierarchy of knowing

Answer 16

data is meaningless. information is important and knowledge is most important.
like there are yello berries. so what?
yellow berries are poisonous! that is information.
knowledge that some yellow berries are poisonous and why is most important - you will not survive just knowing that some random berries are yellow, you need to know that they are poisonous and which ones are.

Question 17

whats a flat file

Answer 17

a simple simple database with only one table

Question 18

what is the role of keys?

Answer 18

to join data